Design And Research On Electromagnetic Properties Of Five-phase Dual-rotor Permanent Magnet Synchronous Motor

In order to satisfy the requirements of high power density and high reliability for the drive motors using in the modern industry, particularly in the fields of aerospace and electric vehicles, a five-phase dual-rotor permanent magnet synchronous motor(FDRPM) is proposed in this paper, which integrates the merits of dual-rotor permanent magnet motor and fault-tolerant permanent magnet motor. Therefore, it owns the advantages of high power density and good fault-tolerant capability at the same time. For this kind of composite structure motor, the following aspects are mainly studied in this paper, and some valuable results have been achieved.First of all, the mathematical models of FDRPM are established for the series connection and parallel connection of inside and outside stator windings respectively, and the mutual inductance matrix existing between them is considered at the same time. It provides a theoretical foundation to achieve the independent control of two motors composited together. Meanwhile, the magnetic coupling problem caused by the structure characteristics of FDRPM is investigated. Influnence laws of the magnetic coupling caused by the stator winding structure, the magnetization type of permanent magnets and the thickness of stator yoke are studied by the finite element simulation under different working conditions, which provide the evidence for the magnetic decoupling design between inner and outer motor units. On this basis, the optimal design of FDRPM is performed by using the combination algorithm of particle swarm optimization and Taguchi(PSO-Taguchi) method. After the global optimization of the permanent magnet pole arc and stator slot open width, the FDRPM obtains the largest average torque under the condition of the torque ripple is minimum.Secondly, to investigate the relationship between the stator magnetomotive force(MMF) and torque under open-circuit fault conditions, the time-space distribution characteristics of the main harmonic and torque performances are analyzed by means of the winding function method and finite element method(FEM) contrastively. Through comparing the results and constructing the equivalent current amplitude function, the similarity relation between the amplitude waveform of the main harmonic and the torque waveform is concluded. At the same time, the torque ripple is analyzed by introducing the equivalent current under open-circuit fault conditions on the basis of the winding function. Then, the fault-tolerant control strategy based on the undisturbed MMF is proposed, and the smooth running is achieved after open-circuit failure. Therefore, it provides an important reference for the high reliable operation of this kind of motor.Thirdly, to research the impact on the rotor losses caused by the changes of stator MMF under open-circuit fault conditions, the harmonic distributions of stator MMF are analyzed by means of winding function, and the finite element anslysis model of rotor losses is established.At the aid of finite element simulation, the rotor eddy-current losses caused by the MMF harmonics are obtained, and the distributions of rotor losses are given under different operating conditions, which provide an important basis for the assessment of loss temperature characteristics of this type of motor.At last, the test system of FDRPM is designed, including the hardware and software section, and the experiments are performed. After the electrical parameters test, it can be found that the prototype is basically consistent with the theoretical design. From the measurement results of no-load back-electromotive force(EMF), it can be known that the actual EMF is similar to the result obtained by the FEM. By comparing the no-load and load EMF, as well as the resultant torque, it can be concluded that the two motors composited together are basically magnetic decoupling. In addition, the simulation results of one phase open-circuit fault show that the fault-tolerant strategy proposed in this paper can realize the goal of adjusting the open-circuit faults. Therefore, the experimental results validate the feasibility of the design method and calculation method proposed in this paper, which offer important reference for the engineering applications of the motor.